Comparing mastoid and posterior cervical muscles vibration effects on eye movement in normal subjects

Abstract

Background and Aim: Vibration is a method for stimulating the vestibular system. This met­hod can unmask asymmetry between two vesti­bular systems (such as unilateral peripheral ves­tibular disorders). The occurrence of vibration-induced nystagmus (VIN) in healthy subjects can affect the diagnosis of patients with uni­lateral peripheral vestibular disorders. Thus, the evaluation of VIN in healthy subjects is critical to help the diagnosis of unilateral peripheral vestibular disorders.
 Methods: This study was carried out on 72 hea­lthy subjects (mean ± SD age: 27.12 ± 4.97 years) in the Auditory and Balance Clinic of Rofeideh Rehabilitation Hospital. Vibration sti­mulation with a frequency of 30 and 100 Hz was used on mastoid and posterior cervical mus­cles (PCMs) and simultaneously eye movements were recorded and analyzed using videonystag­mography.
 Results: The mastoid vibration with a frequ­ency of 30 and 100 Hz, respectively produced VIN in 16.67% and 27.78% of subjects and VIN observed in PCMs vibration with a frequency of 30 and 100 Hz in 4.17% and 9.72% of the subjects.
 Conclusion: The occurrence of VIN in healthy subjects was more probable with mastoid vib­ration in 100 Hz. In this study, VIN was pre­dominantly horizontal, its direction was toward the stimulated side, and its slow phase velocity was lower than 5 deg/s. These criteria could be used for differentiation between normal and abnormal subjects.

The Skull Vibration-induced Nystagmus Test (SVINT) for Vestibular Disorders: A Systematic Review

“…They also emphasize on the patients' clinical history when interpreting the results of a SVINT. Shaabani et al (30) also assessed normal subjects with SVINT, they included subjects with normal VNG and video head impulse test (no caloric test). The mastoid vibration at 100 Hz produced a vibration-induced nystagmus in 27.78% of subjects, with a mean SPV of 2.06 and À2.17 for the left and right mastoid, respectively; the response was never over 5 degrees (30).…”